1. Field of the Invention
The present invention relates to an apparatus and a method for addressing a Time Division Multiple Access (TDMA) noise of a portable terminal. More particularly, the present invention relates to an apparatus for addressing a TDMA noise of a portable terminal induced upon an earphone, and a method thereof.
2. Description of the Related Art
In recent years, with the significant development of information and communication technology and semiconductor technology, the supply and the use of all types of portable terminals have rapidly increased. In particular, recent portable terminals have been developed that converge functions that were traditionally performed by various terminals. A representative example of the portable terminals is a mobile communication terminal that provides various functions, such as a TeleVision (TV) watching function (e.g., mobile broadcasting such as Digital Multimedia Broadcasting (DMB) or Digital Video Broadcasting (DVB)), a music playing function (e.g., Moving Picture Experts Group (MPEG)-1 or MPEG-2 Audio Layer-3 (MP3)), a photographing function, an Internet access function, and a general communication function such as a speech call or message transmission/reception.
Meanwhile, when an earphone is electrically connected to the portable terminal, a ground terminal of the earphone electrically connects with a real ground of the portable terminal. If the ground terminal of the earphone electrically connects with the real ground of the portable terminal, a Time Division Multiple Access (TDMA) noise may be induced upon the earphone through the ground of the portable terminal. That is, a TDMA noise may be heard though the earphone when the earphone is used with the portable terminal during a call. The resulting TDMA noise deteriorates call quality. The following is a simple description of the TDMA noise. A portable terminal transmits and receives a Radio Frequency (RF) signal in a TDMA scheme every predetermined period. That is, the portable terminal activates a power amplifier every transmission period to transmit the RF signal. Power consumption is great in the power amplifier. Due to power consumption by the power amplifier, a voltage drop of a battery occurs every transmission period in the portable terminal. A noise occurring at an audio output terminal due to the voltage drop (i.e., power ripple) that is generated every transmission period is referred to the ‘TDMA noise’.
Further, there is a trend toward using an earphone as an antenna of the portable terminal without including a separate antenna for receiving an RF signal upon providing a radio receiving function. In a case of a portable terminal using an earphone as the antenna for receiving the RF signal, there is a need to address both the TDMA noise and radio receiving performance. Due to this, there is a difficulty in designing a circuit for the portable terminal to reduce the TDMA noise induced in the earphone.